Broad public attention garnered by veterans who commit violent acts after returning to the U.S. from Iraq and Afghanistan demonstrates the urgent need to develop evidence-based approaches to assessing and reducing post-deployment violence risk. Little is known about veterans who have endured combat in Iraq and Afghanistan. Early data indicate many returning soldiers are being diagnosed with posttraumatic stress disorder or alcohol use disorder. Many have experienced traumatic brain injury, as well. Each of these conditions could elevate violence risk. There are no effective empirical tools for screening combat veterans and identifying those individuals at-risk in order to coordinate interventions and prevent these recurring tragedies. This R01 application aims to: 1) identify risk and protective factors empirically related to violent behavior among veterans who have returned from Iraq and Afghanistan;2) examine the link between specific factors related to violence among veterans from previous conflicts and post-deployment violence risk among Iraq and Afghanistan veterans, especially posttraumatic stress disorder, alcohol use disorder, and traumatic brain injury;and 3) develop an evidence-based risk assessment instrument to administer to Iraq and Afghanistan veterans in order to identify those most in need of services. We propose to meet these aims employing two sampling frames. First, we will conduct survey at baseline and one year N=1000 nationally representative veterans who have returned from combat in Iraq or Afghanistan about violent behaviors and factors shown in previous literature to relate to violence among other veterans. Second, we will interview N=300 veterans and a member of their family at baseline and one-year about violence, substance use, family adjustment, posttraumatic stress disorder, and employment status, capitalizing on the infrastructure of the Mid Atlantic Mental Illness Research Education and Clinical Center (MIRECC) in which a registry of veteran, guard/reserve, and active duty personnel from the Iraq and Afghanistan was established at the Durham VA Medical Center in 2005. Risk and protective factors linked to violence in both approaches will be candidates for an actuarial violence risk assessment instrument, which we will develop and validate in a follow-up grant application. The research will yield unique and significant scientific data on the intricate interrelationships between physical aggression, environmental stress, and traumatic events. Further, by following a conceptual and methodological framework already successful for developing violence risk tools in civilian populations, we hope to develop an empirically-validated and clinically-relevant risk assessment instrument to help reduce chances of violence among the thousands of veterans now returning from Iraq and Afghanistan. Public Health Relevance: When veterans become violent, the costs to individuals, their families, their communities, and society are great. Tens of thousands of troops will be returning home from combat in Iraq and Afghanistan in the next few years and, given data showing high rates of post-deployment mental health problems, we urgently need theoretically sophisticated, evidence-based knowledge of which returning veterans are most prone to violence and how the risks they pose to themselves, their families, and others can be effectively managed. By following the guide of scientific literature on civilian risk assessment, the current application aims not only to understand the causes of veteran violence, but also to develop empirically validated and clinically useful tools to assist mental health providers and military staff assess and reduce violence risk among Iraq and Afghanistan veterans.